1. Field of the Invention
The present invention relates to the drilling and completion of well bores in the field of oil and gas recovery. More particularly, this invention relates to an apparatus adapted to improve the alignment of a tubular segments, such as a casing joint or production tubing segment, e.g.) with the tubular string below (e.g. casing string, production string, and the like) extending within a well bore.
2. Description of the Related Art
In the oil and gas industry, well bores are typically drilled by rotating a drill string comprising a plurality of drill pipe segments serially connected and rotating a drill bit thereby creating the well bore. Once the well bore is drilled, tubular casing may be placed in the well bore to protect the well bore from damage over time. The well may then be cemented as desired. Once the casing is in place, production pipe or tubing may also be run within the casing string in the well bore. Such systems may be utilized on land or off-shore.
To assemble the casing string in prior art systems, a derrick or rig is constructed above the well bore. A top drive assembly or drive block may be provided, which may be used to hoist the individual segments above surface. These tubular segments typically are threaded on each end.
An upper portion of the string is extended out of the well bore (i.e. above surface) by a spider having slips on the rig or derrick floor, for example. The slips are adapted to selectively engage the tubular string to prevent the string from falling into the well bore. The tubular string may plurality of segments serially connected end-to-end, described above. The tubular string is located within the well bore W. The upper end of the tubular string is connectable to the lower end of the next segment to be connected. The top drive selectively lowers the segments into contact with the string in the well bore.
In some prior art methods, an operator (a “stabber”) stands on a stabbing board located on the rig above surface. A segment is hoisted off surface via the top drive assembly, and the stabber attempts to align the lower end of the tubular segment extending vertically from the rig or derrick with the string in the well bore below. This may prove to be difficult, as the segments tend to sway, being typically approximately 40 feet long and four to twenty inches in diameter hanging from the top drive assembly.
Once stabber has substantially aligned the tubular segment to be run with the string in the well bore, the segment may be connected to the string. For example, each end of the segments may be threaded. Thus, once the threads of the tubular segment to be run substantially align with the threads on the segment extending above surface from the drill sting, the segment may be rotated utilizing hydraulic tongs. Or the top drive assembly used to rotate the drill string may be utilized to rotate the segment until it is connected to the string. Other conventional connection methods known to one of ordinary skill in the art may further be utilized, such a snap fit, etc.
Alignment of each tubular segment (casing segment or production pipe segment, e.g.) is important for numerous reasons. The tubular segments typically may be forty feet in length, and from two inches to four and a half inches in diameter. Slight misalignment of the segment and the string may weaken the resulting casing string, for example. Greater misalignment of the tubular segment being run and the string in the well bore may compromise the seal between casing segments. If misalignment is significant, cross-threading may occur. The misalignment problem is exacerbated in relatively deep wells, in which the tubing will experience excessive pounds pressure and excessive heat, thus further acting to weaken the seal.
Numerous attempts to improve the alignment of the tubular segments with the string in the well bore during assembly are known. For example, U.S. Pat. No. 4,681,158 to Pennison, incorporated by reference in its entirety herein, for background material, describes the PenniYoke system that includes a casing alignment tool having arms with rollers which selectively clamp end of the casing segment near the well bore (i.e. the lower end of the segment). Once clamped, the hydraulic tongs rotate the segment, the rollers allowing the segment to rotate within the arms. Once the connection is made, the yoke is pivoted away from the string, while another section or segment is hoisted. Similar systems are described in U.S. Pat. No. 5,062,756 to McArthur and U.S. Pat. No. 5,609,457 to Burns.
It has been determined that the use of relatively-complicated systems overhead of workers at surface may be undesirable in some circumstances. Relatively-complicated machinery may increase the cost of the alignment of the tubular segment, and may lead to additional downtime due to the malfunction of complex equipment, increases in the time and cost of transporting the complex equipment to the well site, etc.
Thus, there is a need for an apparatus for improving the alignment of tubular segments with a tubular string in the well bore. It is desirable to provide an alignment tool, which is relatively simple and inexpensive, compared to alternative systems. It is desirable that such a tool substantially align a tubular segment with a string in the well bore with minimal manual intervention. Preferably, the system is simple and easy to operate, and less expensive than present systems. Such a system advantageously would similarly improved ether safety of the alignment operation. Further, the tool would preferably be useable with prior art hydraulic tong systems.
Embodiments of the present invention are directed at overcoming, or reducing and minimizing the effects of, any shortcomings associated with the prior art.